One of several reasons people list to go with the Sportsmobile 4x4 conversion instead of the Quigley conversion is the greatly improved turning radius. However, I'm having trouble finding out what these actually are. My questions/impressions are for a Ford RB van.

It appears that the Quigley 4x4 turning radius is 56'.

I've heard two different numbers for the Sportsmobile turning radius: 39' and 49'. There is obviously a large difference between the two.

Does anyone know which SMB number is correct? Also, if it is 49', then there is a difference between the SMB and Quigley, but not as dynamic as I've been led to believe. Does the 7' really make that much of a difference?

I do not actually have a measurement, but I did test drive one and Jonathan told me that it was 39' for the SMB conversion. I now have a quigley and really wish I would have gotten the smb just for the tighter turning.

SMB used to list 39' curb to curb on their web site. I spent a lot of time with them as they weren't able to get that in real life. The 39' was a typo and it is actually 49'. Their web site now lists it as 49'.
In my opinion, the seven feet is worth it. Depending on how you use your van. My last van, that I built up myself, did have a 39'-6" curb to curb. My SMB will be down close to that when I get back home and work on it. Can't turn too tight, stop too quickly or have too much money....

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Well, I've got my curb to curb down to 45' and that's all I'll be able to get. This is with the 315 tires. I made up a new pitman arm and the restriction to a tighter turn is that my tires are rubbing on the sway bar. The only way to go tighter is to remove the sway bar, go with smaller tires, or more offset to the rims. None of the above is acceptable to me, so I'll be living with the 45 feet. Not too bad.

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Scatter
You can be anything you want on the Internet,
it amazes me that so many choose stupid....